U.S. patent application number 10/695841 was filed with the patent office on 2004-05-13 for preparation method of inorganic compound.
This patent application is currently assigned to Konica Minolta Holdings, Inc.. Invention is credited to Matsuzaka, Syoji, Nakane, Hiroki.
Application Number | 20040091410 10/695841 |
Document ID | / |
Family ID | 32211916 |
Filed Date | 2004-05-13 |
United States Patent
Application |
20040091410 |
Kind Code |
A1 |
Nakane, Hiroki ; et
al. |
May 13, 2004 |
Preparation method of inorganic compound
Abstract
A process of preparing an inorganic compound is disclosed,
comprising the steps of (a) allowing at least an inorganic raw
material compounds (A) and an inorganic raw material compound (B)
which are different in solubility in water to react with each other
in the presence of a reaction solvent with stirring to deposit an
inorganic compound (C), while allowing a part of each of the
compound (A) and compound (B) to exist as a solid; and (b)
separating the inorganic compound (C) from the reaction solvent.
The process is applicable, for example, to preparation of a
phosphor precursor of a rare earth activated alkaline earth metal
fluorohalide.
Inventors: |
Nakane, Hiroki; (Tokyo,
JP) ; Matsuzaka, Syoji; (Tokyo, JP) |
Correspondence
Address: |
MUSERLIAN AND LUCAS AND MERCANTI, LLP
475 PARK AVENUE SOUTH
NEW YORK
NY
10016
US
|
Assignee: |
Konica Minolta Holdings,
Inc.
Tokyo
JP
|
Family ID: |
32211916 |
Appl. No.: |
10/695841 |
Filed: |
October 29, 2003 |
Current U.S.
Class: |
423/263 ;
252/301.4F; 252/301.4H; 252/301.4P; 252/301.5; 252/301.6F;
252/301.6P; 252/301.6S; 423/300; 423/305; 423/326; 423/463;
423/464; 423/466; 423/489; 423/491; 423/497; 423/561.1; 423/566.1;
423/594.13 |
Current CPC
Class: |
C09K 11/7733
20130101 |
Class at
Publication: |
423/263 ;
252/301.60S; 252/301.40P; 252/301.60P; 252/301.40H; 252/301.40F;
252/301.60F; 252/301.5; 423/300; 423/305; 423/326; 423/463;
423/464; 423/466; 423/489; 423/491; 423/497; 423/566.1; 423/561.1;
423/594.13 |
International
Class: |
C09K 011/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2002 |
JP |
JP2002-323647 |
Claims
What is claimed is:
1. A process of preparing an inorganic compound comprising the
steps of: (a) allowing at least an inorganic compounds (A) and an
inorganic compound (B) which are different in solubility in water
to react with each other in the presence of a reaction solvent with
stirring to deposit an inorganic compound (C), while allowing at
least a part of each of the compound (A) and compound (B) to exist
as a solid and (b) separating the inorganic compound (C) from the
reaction solvent.
2. The process of claim 1, wherein the compound (A) exhibits a
solubility in water of not more than 0.1 mol/l at 25.degree. C. and
the compound (B) exhibits a solubility in water of not less than
1.0 mol/l at 25.degree. C., and a solubility of the compound (C) at
25.degree. C. being between the solubility in water of the compound
(A) and that of the compound (B).
3. The process of claim 1, wherein the reaction solvent contains
water in an amount of not more than 900 ml per mol of the compound
(A) and the compound (B).
4. The process of claim 3, wherein said water is contained in an
amount of not more than 380 ml per mol of the compound (A) and the
compound (B).
5. The process of claim 3, wherein said water is contained in an
amount of not more than 200 ml per mol of the compound (A) and the
compound (B).
6. The process of claim 3, wherein the reaction solvent further
contains at least an organic solvent and the compound (A), compound
(B) and compound (C) each exhibit a solubility in the organic
solvent lower than a solubility in water.
7. The process of claim 1, wherein in step (a), the reaction
solvent is added into a reaction vessel and then a solid of the
compound (A) and a solid of the compound (B) are each added into
the reaction vessel, and after completion of addition, a part of
each of the compound (A) and compound (B) exists as a solid in the
reaction vessel.
8. The process of claim 1, wherein in step (a), a solid of one of
the compound (A) and the compound (B) and the reaction solvent are
mixed in the reaction vessel so that the a part of the one of the
compound (A) and the compound (B) exist as a solid and then the
other one of the compound (A) and the compound (B) is further added
to the reaction vessel, and after completion of addition, a part of
each of the compound (A) and compound (B) exists as a solid in the
reaction vessel.
9. The process of claim 1, wherein in step (a), a solid of the
compound (A) and a solid of the compound (B) are added into a
reaction vessel and then the reaction solvent is further added to
the reaction vessel with stirring, and after completion of
addition, a part of each of the compound (A) and compound (B)
exists as a solid in the reaction vessel.
10. The process of claim 7, wherein a solid of one of the compound
(A) and the compound (B) is added into the reaction vessel
containing the reaction solvent and then a solid of the other one
of the compound (A) and the compound (B) is further added
thereto.
11. The process of claim 7, wherein a solid of the compound (A) and
a solid of the compound (B) are simultaneously added to the
reaction vessel containing the reaction solvent.
12. The process of claim 7, wherein a solid of the compound (A) and
a solid of the compound (B) which were previously mixed with each
other are added into the reaction vessel containing the reaction
solvent.
13. The process of claim 7, wherein one of the compound (A) and the
compound (B) which was previously mixed with the reaction solvent
and the other one of the compound (A) and the compound (B) are
simultaneously added to the reaction vessel.
14. The process of claim 8, wherein one of the compound (A) and the
compound (B) is added into the reaction vessel, then, the reaction
solvent is added to the reaction vessel and the other one of the
compound (A) and the compound (B) is further added thereto.
15. The process of claim 8, wherein one of the compound (A) and the
compound (B) is added into the reaction vessel and the other one of
the compound (A) and the compound (B) and the reaction solvent
which were previously mixed with each other are added into the
reaction vessel.
16. The process of claim 9, wherein the reaction solvent which was
previously mixed with an inorganic compound.
17. The process of claim 1, wherein each of the compound (A) and
the compound is mixed with the reaction solvent so that a part of
the compound exists as a solid is added to the reaction vessel.
18. The process of claim 1, wherein the compound (C) is a zinc
sulfide phosphor precursor.
19. The process of claim 1, wherein the compound (C) is a
halophosphate phosphor precursor.
20. The process of claim 1, wherein the compound (C) is a phosphate
phosphor precursor.
21. The process of claim 1, wherein the compound (C) is a silicate
phosphor precursor.
22. The process of claim 1, wherein the compound (C) is a tungstate
phosphor precursor.
23. The process of claim 1, wherein the compound (C) is an
aluminate phosphor precursor.
24. The process of claim 1, wherein the compound (C) is a rare
earth activated alkali metal halide phosphor precursor.
25. The process of claim 1, wherein the compound (C) is a rare
earth activated alkaline earth metal fluorohalide phosphor
precursor.
26. The process of claim 25, wherein the rare earth activated
alkaline earth metal fluorohalide phosphor precursor is represented
by the following formula
(1):Ba.sub.(1-y)(M.sub.2).sub.yFX:aM.sub.1,bLn formula (1)wherein X
represents a halogen element selected from the group consisting of
Cl, Br and I; M.sub.2 represents an alkaline earth metal element
selected from the group consisting of Be, Mg, Sr and Ca; M.sub.1
represents an alkali metal element selected from the group
consisting of Li, Na, K, Rb and Cs; Ln represents a rare earth
element selected from the group consisting of Ce, Pr, Sm, Eu, Gd,
Tb, Tm and Yb; y, a and b are 0.ltoreq.y.ltoreq.0.5,
0.ltoreq.a.ltoreq.0.05 and 0<b.ltoreq.0.2.
27. The process of claim 25, wherein at least one of the compound
(A) and the compound (B) is an inorganic halide compound.
28. The process of claim 25, wherein at least one of the compound
(A) and the compound (B) is a barium halide.
29. The process of claim 25, wherein at least the compound (A) and
the compound (B) are barium halides.
30. The process of claim 29, wherein the inorganic halide compound
is BaF.sub.2 or BaI.sub.2.
31. The process of claim 30, wherein a solid of BaF.sub.2 is added
to the reaction solvent containing BaI.sub.2 of at least 5.1 mol
per liter of the reaction solvent.
32. The process of claim 30, wherein a solid of BaI.sub.2 is added
to the reaction solvent containing BaF.sub.2 of at least 0.1 mol
per liter of the reaction solvent.
33. The process of claim 30, wherein the inorganic halide is
BaF.sub.2 and BaI.sub.2, and an atomic ratio (f/I) of fluorine (f)
contained in the BaF.sub.2 to iodine (i) contained in the BaI.sub.2
is 0.5 to 2.0.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for preparing
inorganic compounds and in particular to a method for preparing
rare earth activated alkaline earth met raw material
(precursor).
BACKGROUND OF THE INVENTION
[0002] There have been known a radiation image recording and
reproducing method using stimulable phosphors as useful diagnosis
means in place of conventional radiography, as described, for
example, in JP-A No. 55-12145 (hereinafter, the term, JP-A means a
Japanese Patent Application Publication). The method employs a
radiation image conversion panel containing stimulable phosphors
(also called cumulative phosphor sheet). Thus, radiation
transmitted through an object or emitted from a test specimen is
absorbed by a stimulable phosphor; subsequently, the stimulable
phosphor is excited with an electromagnetic radiation such as
visible light or ultraviolet light (also called exciting light) to
radiate the accumulated radiation energy in the form of
fluorescence (stimulated emission). The thus emitted fluorescence
is photoelectrically read and converted to electric signals,
followed by reproducing a radiation image of the object or the
specimen, as a visible image, based on the electric signals. After
completion of reading, the conversion panel is subjected to erasing
remained images and used again for radiography.
[0003] This method has advantages that radiation images with a rich
content of information are obtainable at extremely low exposure
dose, as compared to the conventional radiography using the
combination of radiographic film and an intensifying screen. In the
conventional radiography, films are consumed for radiography; on
the contrary, the radiation image conversion panel is repeatedly
used, which is advantageous in terms of natural resource protection
and economic efficiency.
[0004] The radiation image conversion panel comprises a stimulable
phosphor layer provided on a support or a self-supporting
stimulable phosphor layer. The stimulable phosphor layer is usually
composed of a stimulable phosphor dispersed in a binder or
stimulable phosphor coagulants formed by vapor deposition or
calcination. There is also known coagulants which are
interstitially impregnated with polymeric material. Further, a
protective layer comprising polymer film or inorganic
material-deposited film is usually provided on the opposite side of
the support from the phosphor layer.
[0005] There are generally employed stimulable phosphors exhibiting
stimulated emission in the range of 300 to 500 nm, excited by
exciting light within the range of 400 to 900 nm, including rare
earth element activated alkaline earth metal fluorohalide phosphors
described in JP-A Nos. 55-12145, 55-160078, 56-74175, 56-116777,
57-23673, 57-23675, 58-206678, 59-27289, 59-27980, 59-56479 and
59-56480; divalent europium activated alkaline earth metal
fluorohalide phosphors described in JP-A Nos. 59-75200, 60-84381,
60-106752, 60-166379, 60-221483, 60-228592, , 60-228593, 61-23679,
61-120882, 61-120883, 61-120885, 61-235486 and 61-235487; rare
earth element activated oxyhalide phosphors described in JP-A No.
55-12144; cerium activated trivalent metal oxyhalide phosphors
described in JP-A No. 58-69281; bismuth activated alkali metal
halide phosphors described in JP-A No. 60-70484; divalent europium
activated alkaline earth metal halophosphate phosphors described in
JP-A Nos. 60-141783 and 60-157100; divalent europium activated
alkaline earth metal haloborate phosphors described in JP-A No.
60-157099; divalent europium activated alkaline earth metal
hydrogen halide phosphors described in JP-A No. 60-217354; cerium
activated rare earth combined halide phosphors described in JP-A
Nos. 61-21173 and 61-21182; cerium activated rare earth
halophosphate phosphors described in JP-A No. 61-40390; divalent
europium activated cerium-rubidium halide phosphors described in
JP-A No. 60-78151; and divalent europium activated combined halide
phosphors described in JP-A No. 60-78151. Specifically, there are
known stimulable phosphors such as iodide containing divalent
europium activated alkaline earth metal fluorohalide phosphors,
iodide containing rare earth metal activated oxyhalide phosphors,
and iodide containing bismuth activated alkali metal halide
phosphors.
[0006] Methods for preparing stimulable phosphors include a solid
phase process or so-called calcination method, and a liquid phase
process in which a crystalline stimulable phosphor precursor is
prepared in the liquid phase and the precursor is further calcined
to obtain a stimulable phosphor. The solid phase process or
calcination method necessitates pulverization after calcination,
producing problems that it is difficult to control the grain shape
or size which affects sensitivity or imaging performance. Fine
particle formation of stimulable phosphors is an effective means to
enhance image quality in radiation image conversion panels using
stimulable phosphors.
[0007] JP-A 7-233369 and 9-291278 disclosed preparation of a
stimulable phosphor in a liquid process, in which a fine
particulate stimulable phosphor precursor was obtained by
controlling the concentration of solution of phosphor raw material,
providing a useful preparation method of stimulable phosphor
precursors.
[0008] A precursor of an alkaline earth metal fluorohalide
stimulable phosphor, prepared by the method described above was
advantageous in luminance and graininess but preparation of a
crystalline precursor in the liquid phase included the following
problems. Thus, as described in JP-A Nos. 10-88125 and 9-291278,
the following methods are useful:
[0009] (1) a method in which barium halide is dissolved in water or
an organic solvent, followed by adding an inorganic fluoride
solution with stirring;
[0010] (2) a method in which ammonium fluoride is dissolved in
water, followed by adding barium halide with stirring.
[0011] However, the method (1) necessitated to allow a barium
halide to be present in excess in the solution, often resulting in
a reduced stoichiometrical ratio of barium fluorohalide obtained
from the solution to barium halide, ca. 0.4. Thus, the yield of an
alkaline earth metal fluoroiodide stimulable phosphor was often
about 40% of a barium halide provided.
[0012] The method (2) also necessitated a barium halide in excess
for an inorganic fluoride, leading to a low yield. As described
above, synthesis of a stimulable phosphor precursor of an alkaline
earth metal fluorohalide exhibited an extremely low yield, having
problems such as low productivity.
[0013] To enhance the yield of a stimulable phosphor precursor of a
rare earth metal activated alkaline earth metal fluorohalide,
specifically, alkaline earth metal fluoroiodide stimulable phosphor
precursor, JP-A No. 11-29324 disclosed a method of preparing square
crystals of a rare earth element containing fluoroiodide,
comprising a basic composition of BaFI:xLn (in which Ln is a rare
earth element selected from Ce, Pr, Sm, Eu, Gd, Tb, Tm and Yb;
0<x.ltoreq.0.1), in which a reaction mixture having a specified
concentration was concentrated after adding a fluorine source.
However, it was proved by the inventors of this application that
although square-form BaFi crystals were formed according to the
method taught in the foregoing patent document, concentration was
performed by natural evaporation, leading to lowered productivity
unacceptable in practical use. It was further proved that the thus
obtained square-form crystals had relatively large sizes and a
broad size distribution, resulting in inferior image qualities,
which were unacceptable in practical use.
[0014] There were further disclosed methods for enhancing the yield
of a stimulable phosphor precursor of a rare earth metal activated
alkaline earth metal fluorohalide, specifically, alkaline earth
metal fluoroiodide stimulable phosphor precursor, for example, in
JP-A No. 2002-38143, in which the stoichiometrical ratio of the
separated barium fluoride to the provided barium iodide was ca.
0.6, thus, the yield of an alkaline earth metal fluoroiodide
stimulable phosphor being at an insufficient value of 60%.
[0015] In the foregoing methods of preparing phosphor precursors in
the liquid phase, problems arose with a barium halide being needed
in excess as raw material, leading to substantial waste of raw
material, which was not preferable in terms of production
efficiency. Furthermore, unreacted halide ions which remained in
excess in the reaction system were incorporated into precipitates
of the phosphor precursor, resulting in deteriorated performance,
so that washing had to be carefully performed when separating the
precursor from the reaction mixture solution.
SUMMARY OF THE INVENTION
[0016] Accordingly, it is an object of the present invention to
provide a method for preparing inorganic compounds with high yield
and in particular to a method for preparing a precursor of
crystalline rare earth-activated alkaline earth metal fluorohalide
phosphor, which is formed at a high yield by effectively employing
raw materials such as halide ions and alkaline earth metal ions and
in which residues on reaction are minimized and washing can be
easily carried out when separating the precursor from the reaction
mixture solution.
[0017] The foregoing object of the invention can be accomplished by
the following constitutions:
[0018] 1. A process of preparing an inorganic compound comprising
the steps of:
[0019] (a) allowing at least an inorganic compounds (A) and an
inorganic compound (B) which are different in solubility in water
to react with each other in the presence of a reaction solvent with
stirring to deposit an inorganic compound (C), while at least a
part of each of the compound (A) and at least a part of the
compound (B) being allowed to exist as solids and
[0020] (b) separating the inorganic compound (C) from the reaction
solvent.
DETAILED DESCRIPTION OF THE INVENTION
[0021] In the invention, the process of preparing an inorganic
compound through a liquid-phase reaction comprises (i) allowing at
least two inorganic compounds (A) and (B) differing in solubility
in water (for example, a relatively sparingly water-soluble
inorganic raw material compound and a relatively easily
water-soluble inorganic raw material compound) to react with each
other in the presence of a reaction solvent with stirring to form
an inorganic compound (C) precipitate and (ii) separating the
inorganic compound (C) from the reaction solvent, while a part of
the compound (A) and a part of the compound (B)being allowed to
exist as solids. Thus, the inorganic compound (A) and the inorganic
compound (B), each of which is in an amount exceeding its
solubility in the solvent and is, in a part, a solid, are allowed
to react with each other through the liquid-phase reaction in the
presence of a reaction solvent to form an inorganic compound (C),
which is in an amount exceeding its solubility in the solvent and
is, in a part, a solid; and the solvent is present in a minimum
amount necessary to maintain fluidity of the reaction mixture.
[0022] One aspect of this invention is that when at least two
inorganic compounds as raw material are reacted with each other to
form an inorganic compound as a product, reaction is conducted
under the condition that inorganic compounds (A), (B) as raw
material and an inorganic compound (C) as a reaction product are
each in amounts exceeding the respective saturated concentrations,
i.e., any one of the inorganic compounds (A), (B) and (C) partially
exists in a solid form, concurrently in the presence of a reaction
solvent in at least an amount capable of maintaining fluidity of
the reaction mixture (or in an amount of capable of slurrying the
reaction mixture). Thereby, the respective inorganic compounds as
raw material effectively contribute the reaction, forming easily
washable inorganic compound as a reaction product at a relatively
high yield.
[0023] The expression, any one of the inorganic compounds (A), (B)
and (C) partially existing in a solid form means that a part of
each of the respective inorganic compounds is in a solid such as a
powdery form or massive form and a reaction solvent is provided in
an amount necessary to maintain fluidity of reaction mother liquor
or slurrying the reaction mixture. In other words, inorganic
compounds as raw material are supplied in large amounts exceeding
saturated concentrations and the compounds exist in a solid form
without being dissolved in the reaction solution. Herein, the
inorganic compounds as raw material are those which supply main
component elements forming the moiety of an inorganic compound as a
product, so that inorganic compounds added as a modifier, such as
an activator or dopant are excluded from the inorganic compounds as
raw material. The inorganic compounds as raw material include their
inorganic salts and hydrates.
[0024] In this invention, a sparingly water-soluble raw material,
inorganic compound (A) is reacted with and an easily water-soluble
raw material, inorganic compound (B) in the presence of a reaction
solvent. Solvents usable as the reaction solvent include, for
example, water, alcohol type organic solvents (e.g., methanol,
ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol,
2-methyl-2-butanol, cyclohexanol), ether type organic solvents
(e.g., tetrahydrofuran, diisopropyl ether, ethylene glycol
monomethyl ether, ethylene glycol monopropyl ether, ethylene glycol
dimethyl ether, ethylene glycol monobutyl ether, anisole, dioxane,
phenetol), ketone type organic solvents (e.g., acetone, methyl
ethyl ketone, cyclohexanone), ester type organic solvents (e.g.,
propyl formate, butyl formate, methyl acetate, ethyl acetate,
propyl acetate, ethylene glycol diacetate), and hydrocarbon type
organic solvents (e.g., cyclohexane, cyclopentane, cycloheptane). A
mixture of water and the foregoing organic solvents is preferred as
a reaction solvent used in the invention. A mixture of water and
the foregoing alcohol type solvents is more preferred, in which the
content of water (the proportion of water by volume) is preferably
no more than 80%, more preferably no more than 50%, and still more
preferably no more than 30% by volume.
[0025] In this invention, at least one of reaction solvents is
preferably one which has lower solubility than water for the
inorganic compounds as raw material and the inorganic compound as
product. Depending on the kind of inorganic compounds used as raw
material and inorganic compounds as a product, the reaction solvent
used in this invention is optimally selected from the fore going
solvents (preferably organic solvents).
[0026] In the foregoing preparation method of this invention, it is
preferred that an inorganic compound (A') having a solubility in
water of not more than 0.1 mol/l and an inorganic compound (B')
having a solubility in water of not less than 1 mol/l are used as
the foregoing inorganic raw material compounds A and B,
respectively, and the solubility in water of an inorganic compound
as the reaction product falls between the solubility of the
compound (A') and that of the compound (B'). Conducting the
reaction under the condition described above leads to easy washing
and effective contribution of the respective raw material compounds
to the reaction, producing the inorganic compound at high
yield.
[0027] In one preferred embodiment of this invention, at least a
part of the reaction solvent is water, and the amount of water is
not more than 900 ml, preferably not more than 380 ml, and more
preferably not more than 200 ml per mol of the entire raw material
inorganic compounds. Performing the reaction under the condition
described above renders easy washing and causes inorganic raw
material compounds to effectively contribute the reaction, making
it possible to obtain an inorganic product compound at high
yield.
[0028] The present invention concerns a method for preparing an
inorganic compound (designated C) through liquid phase reaction by
allowing inorganic raw material compounds differing in solubility
in water to react with each other, for example, by allowing at
least a relatively sparingly water-soluble inorganic raw material
compound (designated A) to react with at least a relatively
water-soluble inorganic raw material compound (designated B) in the
presence of water, wherein addition of the inorganic compounds (A
and B), which depends on the kind of the compound, can be selected
from various forms and addition patterns. Preferred examples of the
embodiment of the form or addition of the inorganic compounds (A
and B) are described below, but the invention is by no means
limited to these.
[0029] Pattern of addition (1): a preparation process, in which all
of inorganic compounds (A and B) are added in a solid form to a
reaction vessel containing a reaction solvent to form reaction
mother liquor containing solids of the inorganic compounds and
then, reaction is allowed with stirring to form inorganic compound
(C), while allowing at least a part of each of the inorganic
compounds (A and B) exists in a solid form;
[0030] Pattern of addition (2): a preparation process, in which at
least one of inorganic compounds (A and B) is added together with a
reaction solvent to a reaction vessel so that at least a part of
the one of inorganic compounds exists in a solid form and then, the
other one of the inorganic compounds (A and B) is added thereto in
a solid form to undergo reaction with stirring, while allowing at
least a part of each of the inorganic compounds (A and B) to exist
in a solid form;
[0031] Pattern of addition (3): a preparation process, in which at
least inorganic compounds (A and B) are added in a solid form to a
reaction vessel and mixed, then, a reaction solvent is further
added thereto so that at least a part of each of the inorganic
compounds (A and B) exists in a solid form and reaction is
undergone with stirring to form inorganic compound (C), while
allowing at least a part of each of the inorganic compounds (A, B)
to exist in a solid form;
[0032] Pattern of addition (4): a preparation process, in which a
reaction solvent is added to a reaction vessel and then, at least
one of inorganic compounds (A and B) is added in a solid form to
the reaction vessel with stirring, followed by adding the other one
of inorganic compounds (A and B) in a solid form so that at least a
part of each of the inorganic compounds (A and B) exists in a solid
form, then, reaction is undergone with stirring to form inorganic
compound (C), while allowing at least a part of each of the
inorganic compounds (A, B) to exist in a solid form;
[0033] Pattern of addition (5): a preparation process, in which at
least inorganic compounds (A and B) are simultaneously added in a
solid form to a reaction vessel containing a reaction solvent with
stirring to undergo reaction to form inorganic compound (C), while
allowing at least a part of each of the inorganic compounds (A, B)
to exist in a solid form;
[0034] Pattern of addition (6): a preparation process, in which a
reaction solvent is added to a reaction vessel and thereto,
inorganic compounds (A and B), which were previously mixed in a
solid form, are added with stirring to undergo reaction to form
inorganic compound (C), while allowing at least a part of each of
the inorganic compounds (A and B) to exist in a solid form;
[0035] Pattern of addition (7): a preparation process, in which at
least inorganic compounds (A and B) are simultaneously added to a
reaction vessel provided with a stirring function and at least one
of the inorganic compounds (A, B) forms a mixture with the reaction
solvent, then reaction is undergone to form inorganic compound (C),
while allowing at least a part of each of the inorganic compounds
(A and B) to exist in a solid form;
[0036] Pattern of addition (8): a preparation process, in which a
reaction solvent is added to a reaction vessel containing at least
one of inorganic compounds (A, B) in a solid form, while stirring
and then, the other one of the inorganic compound (A, B) is added
thereto in a solid form to undergo reaction to form inorganic
compound (C), while allowing at least a part of each of the
inorganic compounds (A and B) to exist in a solid form;
[0037] Pattern of addition (9): a preparation process, in which one
of inorganic compound (A and B) which was previously mixed with a
reaction solvent is added to a reaction vessel containing the other
one of inorganic compounds (A and B) in a solid form with stirring
to undergo reaction to form inorganic compound (C), while allowing
at least a part of each of the inorganic compounds (A and B) to
exist in a solid form; Pattern of addition (10): a preparation
process, in which at least inorganic compounds (A and B) in a solid
form are mixed with stirring in a reaction vessel and further
thereto, a mixture of at least one of the inorganic compounds (A,
B) and reaction solvent is added to undergo reaction to form
inorganic compound (C), while allowing at least a part of each of
the inorganic compounds (A and B) to exist in a solid form;
[0038] Pattern of addition (11): any one of the foregoing
preparation processes, in which at least one of the inorganic
compounds (A and B) is comprised of a saturated solution of the
inorganic compound and a solid.
[0039] The preparation process is optimally selected from the
foregoing processes, depending on the kind of the inorganic
compound (C) or desired characteristics, such as achieved grain
size, grain size distribution and property of inorganic compound
(C).
[0040] The preparation process of inorganic compounds, according to
this invention is applicable to commonly known inorganic compounds,
and to effectively display advantages of the invention, examples of
preferred inorganic compounds include a zinc sulfide type phosphor
precursor, a halophosphate type phosphor precursor, a phosphate
type phosphor precursor, a silicate type phosphor precursor, a
tungstate type phosphor precursor, an aluminate type phosphor
precursor, and a rare earth activated alkaline earth metal halide
type phosphor precursor. It is specifically preferred to apply to
preparation of rare earth activated alkaline earth metal halide
type phosphor precursors.
[0041] Next, preparation of a rare earth activated alkaline earth
metal halide phosphor precursor will be described below. Rare earth
activated alkaline earth metal halide phosphor precursors relating
to this invention are preferably a rare earth activated alkaline
earth metal fluorohalide phosphor precursor, and more preferably a
rare earth activated alkaline earth metal fluorohalide stimulable
phosphor precursor represented by the following formula (1):
Ba.sub.(1-y)(M.sub.2).sub.yFX:aM.sub.1,bLn formula (1)
[0042] wherein X represents a halogen element selected from the
group consisting of Cl, Br and I; M.sub.2 represents an alkaline
earth metal element selected from the group consisting of Be, Mg,
Sr and Ca; M.sub.1 represents an alkali metal element selected from
the group consisting of Li, Na, K, Rb and Cs; Ln represents a rare
earth element selected from the group consisting of Ce, Pr, Sm, Eu,
Gd, Tb, Tm and Yb; y, a and b are 0.ltoreq.y.ltoreq.0.5,
0.ltoreq.a.ltoreq.0.05 and 0<b.ltoreq.0.2.
[0043] The stimulable phosphor precursor described above refers to
a state in which the compound represented by the foregoing formula
(1) has not yet been subjected to heating at a temperature of
400.degree. C. or more.
[0044] A process of preparing a crystalline rare earth-activated
alkaline earth metal fluorohalide preferably comprises a
precipitation step to allow a rare earth-activated alkaline earth
metal fluorohalide to precipitate in reaction mother liquor and a
post-step subsequent to the precipitation step which comprises
separating precipitates from the reaction mother liquor, as
described below.
[0045] Next, the foregoing respective steps are concretely
described below.
[0046] Precipitation Step
[0047] The precipitation step is a process of allowing an inorganic
halide and barium halide to react with each other to form a
crystalline barium fluorohalide (BaFX) precipitate as a precursor
of a stimulable phosphor.
[0048] Halogen elements of the barium halide include F, Cl, Br and
I. F, Br and I are preferred when BaFx crystals are used as
phosphor material. Preferred barium halides usable as raw material
inorganic compound include barium fluoride, barium chloride, barium
bromide, barium iodide an their hydrides. Halogen elements are
optionally selected, depending on an intended product and plural
halide elements are also usable. Barium halides are not limited to
the foregoing halides and other barium halides are also usable in
this invention.
[0049] One feature concerning this invention is that when mixed
with a reaction solvent, the amount of a barium halide is more than
its saturated concentration and a part of it exists in a solid form
in solution. For example, the amount of barium fluoride is more
than 0.01 moles per liter of solution (also denoted as mol/l), that
of barium chloride or barium bromide is more than 2.6 mol/l, and
that of barium iodide is more than 5.1 mol/l. Specifically, barium
fluoride is preferably more than 0.1 mol/l, and more preferably
more than 1.0 mol/l; barium iodide is preferably more than 6.0
mol/l, and more preferably more than 7.0 mol/l. The upper limit of
a barium halide in the reaction mixture, which is variable with the
kind of a solvent, is a quantity at which fluidity of the reaction
mixture is lost or stirring the reaction mixture becomes
infeasible. As described above, the amount (expressed in mol/l)
means a quantity of an inorganic compound as raw material,
expressed in terms of the number of moles of the inorganic compound
per liter of a solvent.
[0050] Examples of inorganic halides usable in this invention
include ammonium fluoride, sodium fluoride, potassium fluoride,
calcium fluoride, magnesium fluoride, strontium fluoride, barium
fluoride, and bromides and iodides in which the foregoing fluorides
were replaced by bromides or iodides. Of these halides described
above, ammonium fluoride, ammonium chloride, ammonium bromide,
ammonium iodide, barium fluoride, barium chloride, barium bromide,
and barium iodide are preferred. Halogen elements are optionally
selected, depending on an intended product and plural halide
elements are also usable. Inorganic halides are not limited to the
foregoing halides and other inorganic halides are also usable in
this invention.
[0051] When mixed with a reaction solvent, the amount of an
inorganic halide is more than its saturated concentration and a
part of it preferably exists in a solid form in solution. The upper
limit of an inorganic halide in the reaction mixture, which is
variable with the kind of a solvent used therein, is a quantity at
which fluidity of the reaction mixture is lost or stirring the
reaction mixture becomes infeasible. The molar ratio of fluorine to
other halogens contained in all of inorganic compounds as raw
material (e.g., molar ratio of fluorine/bromine and iodine in BaFX)
is preferably 0.5 to 2.0, more preferably 0.65 to 1.54, and still
more preferably 0.75 to 1.33. The molar ratio of fluorine to barium
contained in all of inorganic compounds as raw material (e.g.,
molar ratio of fluorine/barium in BaFX) is preferably 0.5 to 2.0,
more preferably 0.65 to 1.54, and still more preferably 0.75 to
1.33.
[0052] An inorganic halide, barium halide and reaction solvent can
be added in accordance with addition patterns described earlier or
in other various manners. Addition may be carried out continuously
or intermittently (i.e., after continuing addition over a
prescribed period of time, the addition stops over a period of time
and such sequence is repeated). For example, in the case of plural
inorganic compounds used as raw material, the inorganic compounds
are added alternately and intermittently.
[0053] Activators are further added to provide fluorescence or
phosphorescence properties to BaFx crystals obtained in this
invention. An activator may be added at any time and is preferably
added to a solvent simultaneously with or before addition of
inorganic compounds as raw material. Alternatively, the activator
may be added to inorganic compounds as raw material. Preferred
activators include, for example, halides of Ce, Pr, Sm, Eu, Gd, Tb,
Tm and Yb. Halogen elements are optionally selected, depending on
an intended product. In the case of BAFI, for example, europium
iodide or cerium iodide is preferable. The activator content can be
optimized according to intended performance.
[0054] Other components can optionally be selected from alkali
metals such as Li, Na, K, Rb and Cs and alkaline earth metals such
as Mg, Ca and Sr. These compounds can be added similarly to the
foregoing activators with respect to addition manner, timing and
amount.
[0055] When the foregoing component compounds are mixed to form a
precipitate, the reaction mixture is maintained preferably at a
temperature (reaction temperature) of 0 to 100.degree. C. There may
further be added a small amount of an acid, ammonia, water-soluble
polymer or a surfactant.
[0056] Separation Step
[0057] The separation step is a process of separating a crystalline
BaFX precipitate formed through the foregoing precipitation step,
from reaction mixture (or reaction mother liquor), which is
preferably provided as a post-step subsequent to the precipitation
step. The formed precipitate is separated by filtration or
centrifugal separation, followed by being sufficiently washed with
organic solvents such as ethanol and isopropyl alcohol and
dried.
[0058] A precursor of a rare earth activated alkali metal halide
phosphor, obtained according to the method of this invention
exhibits superior washing efficiency, in which washing is achieved
using a solvent in a smaller amount and at a higher cleaning
degree, as compared to the conventional liquid phase process.
[0059] A rare earth activated alkali metal halide phosphor
precursor obtained according to this invention preferably has an
average grain size of 1 to 10 .mu.m. The average grain size is an
average value of sphere equivalent diameters (diameter of a sphere
having a volume equivalent to the grain) of 200 grains selected at
random from an electron micrograph of the grains.
[0060] The thus obtained rare earth activated alkali metal halide
phosphor precursor is further subjected to calcination according to
methods known in the art to obtain stimulable phosphor particles.
The obtained stimulable phosphor particles are used for a radiation
image conversion panel.
EXAMPLES
[0061] The present invention will be further described based on
examples but embodiments of the invention are by no means limited
to these.
Example 1
Preparation of Stimulable Phosphor Precursor
[0062] Stimulable phosphor precursors were synthesized according to
the following manner.
[0063] Synthesis of Stimulable Phosphor Precursor 1
[0064] A precursor of stimulable phosphor, europium activated
barium fluoroiodide was prepared according to the following
procedure. T a reaction vessel were added 2380 ml of aqueous
BaI.sub.2 solution (4.2 mol/l) and 27 ml of aqueous EuI.sub.3
solution (0.2 mol/l). Reaction mother liquor in the reaction vessel
was maintained at a temperature of 83.degree. C. with stirring and
further thereto 200 ml of an aqueous ammonium fluoride solution (13
mol/l) was added over a period of 30 min. using a roller pump to
form a precipitate. After completion of addition, the reaction
mixture was further stirred with maintaining the temperature for 2
hr. to ripen the precipitate. Subsequently, the precipitate was
separated by filtration, washed with 1600 ml of ethanol and dried
in vacuo to obtain a precursor of europium activated barium
fluoroiodide stimulable phosphor (precursor 1).
[0065] Synthesis of Stimulable Phosphor Precursor 2
[0066] Synthesis was conducted in accordance with the
afore-mentioned pattern of addition (8). Thus, 99.4 g of powdery
BaF.sub.2 was added to a 1 liter conical reaction vessel provided
with stirrer. Then, 1.2 g of EuI.sub.3 dispersed in 82 ml reaction
solvent (ethanol/water =3/1) was added thereto and slurried with
solid powdery BaF.sub.2, while stirring. Thus obtained BaF.sub.2
slurry was maintained at 60.degree. C. Subsequently, to the
BaF.sub.2 slurry, 296.0 g of powdery BaI.sub.2.2H.sub.2O was in
limited amounts and slurried with stirring. The reaction mixture
was further maintained at 60.degree. C. for 2 hr. with stirring to
form crystals of BaFI:Eu. The formed crystals were separated by
filtration, washed with 1600 ml of ethanol and dried in vacuo to
obtain a precursor of europium activated barium fluoroiodide
stimulable phosphor (denoted as precursor 2).
[0067] Synthesis of Stimulable Phosphor Precursor 3
[0068] Synthesis was conducted in accordance with the
afore-mentioned pattern of addition (1). Thus, 1.2 g of EuI.sub.3
dispersed in 82 ml reaction solvent (ethanol/water =3/1) was added
to a 1 liter conical reaction vessel provided with stirrer and 99.4
g of powdery BaF.sub.2 was further added thereto and slurried with
stirring, while being maintained at 60.degree. C. Subsequently, to
the slurry, 296.0 g of powdery BaI.sub.2.2H.sub.2O was in limited
amounts and slurried with stirring. The reaction mixture (slurry)
was further maintained at 60.degree. C. for 2 hr. with stirring to
form crystals of BaFI:Eu. The formed crystals were separated by
filtration, washed with 1600 ml of ethanol and dried in vacuo to
obtain a precursor of europium activated barium fluoroiodide
stimulable phosphor (denoted as precursor 3).
[0069] Synthesis of Stimulable Phosphor Precursor 4
[0070] Synthesis was conducted in accordance with the
afore-mentioned pattern of addition (3). Thus, to a 1 liter conical
reaction vessel provided with stirrer were simultaneously added
99.4 g of powdery BaF.sub.2 and 296.0 g of powdery
BaI.sub.2.2H.sub.2O. After mixing with stirring, 1.2 g of EuI.sub.3
dispersed in 82 ml reaction solvent (ethanol/water =3/1) was added
thereto, mixed with powdery BaF.sub.2 and BaI.sub.2.2H.sub.2O and
slurried with stirring. The reaction mixture (slurry) was further
maintained at 60.degree. C. for 2 hr. with stirring to form
crystals of BaFI:Eu. The formed crystals were separated by
filtration, washed with 1600 ml of ethanol and dried in vacuo to
obtain a precursor of europium activated barium fluoroiodide
stimulable phosphor (denoted as precursor 4).
[0071] Synthesis of Stimulable Phosphor Precursor 5
[0072] Synthesis was conducted in accordance with the
afore-mentioned pattern of addition (6). Thus, to a 1 liter conical
reaction vessel provided with stirrer was added 1.2 g of EuI.sub.3
dispersed in 82 ml reaction solvent (ethanol/water =3/1) and
further thereto, a powdery mixture of 99.4 g of BaF.sub.2 and 296.0
g of BaI.sub.2.2H.sub.2O was added, mixed and slurried with
stirring. The reaction mixture (slurry) was further maintained at
60.degree. C. for 2 hr. with stirring to form crystals of BaFI:Eu.
The formed crystals were separated by filtration, washed with 1600
ml of ethanol and dried in vacuo to obtain a precursor of europium
activated barium fluoroiodide stimulable phosphor (denoted as
precursor 5).
[0073] Synthesis of Stimulable Phosphor Precursor 6
[0074] Synthesis was conducted in accordance with the
afore-mentioned pattern of addition (7). Thus, to a 1 liter conical
reaction vessel provided with stirrer, a slurry obtained by mixing
99.4 g of powdery BaF.sub.2 with 1.2 g of EuI.sub.3 dispersed in 82
ml reaction solvent (ethanol/water =3/1) and 296.0 g of powdery
BaI.sub.2.2H.sub.2O were simultaneously added and slurried with
stirring. The reaction mixture (slurry) was further maintained at
60.degree. C. for 2 hr. with stirring to form crystals of BaFI:Eu.
The formed crystals were separated by filtration, washed with 1600
ml of ethanol and dried in vacuo to obtain a precursor of europium
activated barium fluoroiodide stimulable phosphor (denoted as
precursor 6).
[0075] Synthesis of Stimulable Phosphor Precursor 7
[0076] Synthesis was conducted in accordance with the
afore-mentioned pattern of addition (9). Thus, to a 1 liter conical
reaction vessel provided with stirrer, 99.4 g of powdery BaF.sub.2
was added, then, 1.2 g of EuI.sub.3 dispersed in 82 ml reaction
solvent (ethanol/water =3/1) and 296.0 g of powdery
BaI.sub.2.2H.sub.2O were added and slurried with stirring. The
reaction mixture (slurry) was further maintained at 60.degree. C.
for 2 hr. with stirring to form crystals of BaFI:Eu. The formed
crystals were separated by filtration, washed with 1600 ml of
ethanol and dried in vacuo to obtain a precursor of europium
activated barium fluoroiodide stimulable phosphor (denoted as
precursor 7).
[0077] Synthesis of Stimulable Phosphor Precursor 8
[0078] Synthesis was conducted in accordance with the
afore-mentioned pattern of addition (4). Thus, to a 1 liter conical
reaction vessel provided with stirrer, 1.2 g of EuI.sub.3 dispersed
in 82 ml reaction solvent (ethanol/water =3/1) was added and then,
296.0 g of powdery BaI.sub.2.2H.sub.2O was added and slurried with
stirring. Further thereto, 99.4 g of powdery BaF.sub.2 was added
and slurried with stirring. The reaction mixture (slurry) was
further maintained at 60.degree. C. for 2 hr. with stirring to form
crystals of BaFI:Eu. The formed crystals were separated by
filtration, washed with 1600 ml of ethanol and dried in vacuo to
obtain a precursor of europium activated barium fluoroiodide
stimulable phosphor (denoted as precursor 8).
[0079] Synthesis of Stimulable Phosphor Precursor 9
[0080] Similarly to the foregoing precursor 2, synthesis was
conducted in accordance with the afore-mentioned pattern of
addition (8), except that the amount of added BaF.sub.2 was changed
to 121.5 g. A precursor of europium activated barium fluoroiodide
stimulable phosphor was thus obtained (precursor 9).
[0081] Synthesis of Stimulable Phosphor Precursor 10
[0082] Similarly to the foregoing precursor 2, synthesis was
conducted in accordance with the afore-mentioned pattern of
addition (8), except that the amount of the reaction solvent
(ethanol/water =3/1) was changed to 164 ml. A precursor of europium
activated barium fluoroiodide stimulable phosphor was thus obtained
(precursor 10).
[0083] Synthesis of Stimulable Phosphor Precursor 11
[0084] Similarly to the foregoing precursor 2, synthesis was
conducted in accordance with the afore-mentioned pattern of
addition (8), except that the amount of the reaction solvent
(ethanol/water =3/1) was changed to 50 ml. A precursor of europium
activated barium fluoroiodide stimulable phosphor was thus obtained
(precursor 11).
[0085] Synthesis of Stimulable Phosphor Precursor 12
[0086] Similarly to the foregoing precursor 2, synthesis was
conducted in accordance with the afore-mentioned pattern of
addition (8), except that the ratio of ethanol/water of the
reaction solvent was changed to ethanol/water =3/2. A precursor of
europium activated barium fluoroiodide stimulable phosphor was thus
obtained (precursor 12).
[0087] Synthesis of Stimulable Phosphor Precursor 13
[0088] Similarly to the foregoing precursor 2, synthesis was
conducted in accordance with the afore-mentioned pattern of
addition (8), except that the amount of the reaction solvent
(ethanol/water =3/1) was changed to 560 ml to dissolver all of
powdery BaI.sub.2.2H.sub.2O. A precursor of europium activated
barium fluoroiodide stimulable phosphor was thus obtained
(precursor 13).
[0089] Synthesis of Stimulable Phosphor Precursor 14
[0090] To a pressure-tight reaction vessel were added 2500 ml of an
aqueous BaI.sub.2 solution (4 mol/l) and 26.5 ml of an aqueous
EuI.sub.3 solution (0.2 mol/l). Further thereto, 992 g of potassium
iodide was added and maintained at 83.degree. C. with stirring.
Ten, 600 ml of an aqueous ammonium fluoride solution (10 mol/1) was
added thereto using a roller pump to form a precipitate. The
reaction mixture was further stirred for 90 min. Thereafter, the
precipitate was separated by filtration and washed with ethanol to
obtain a precursor of europium activated barium fluoroiodide
stimulable phosphor (denoted as precursor 14).
[0091] Synthesis of Stimulable Phosphor Precursor 15
[0092] To a 300 ml separable beaker, 150 ml of an aqueous BaI.sub.2
solution (4 mol/l) was added, then, 3 ml of a EuI.sub.3 solution
(0.1 mol/l) and 47 ml of water were added thereto, and 50 ml of an
aqueous ammonium fluoride solution (6 mol/1) was further added and
maintained at 80 .degree. C. To the thus prepared solution, 50 g of
Teflon (R) boiling stone (available from Chem-Wear Co.) was added
and reaction continued for 2 hr. with stirring, while being
evacuated with an aspirator to obtain a precipitate of europium
activated barium fluoroiodide phosphor precursor (particulate
BaFI:Eu). After completion of reaction, Teflon (R) boiling stone
was separated using a stainless steel mesh with a 1 mm aperture and
then, the precipitate was separated by suction filtration using
filter paper. The separated precipitate was washed by uniformly
sprinkling 300 ml of isopropyl alcohol (IPA) and dried in vacuo at
150.degree. C. over a period of 2 hr. to obtain a precursor of
europium activated barium fluoroiodide stimulable phosphor (denoted
as precursor 15).
Evaluation of Stimulable Phosphor Precursor
[0093] Determination of Yield
[0094] Amounts of Ba added in the respective syntheses were
determined and amounts of Ba contained in the respective europium
activated barium fluoroiodide phosphor precursors were determined
by X-ray diffractometry to calculate the yield for the respective
syntheses.
[0095] Measurement of Washing Degree
[0096] The free-iodine content of the europium activated barium
fluoroiodide phosphor precursor was determined as a measure of
washing degree, according to the following procedure. The less
free0iodine content indicates the higher washing degree.
[0097] Each of the prepared particulate precursors of europium
activated barium fluoroiodide phosphors was precisely weighed by 1
g, added to 10 ml ethanol and dispersed using a ultrasonic
homogenizer over a period of 30 sec. to prepare dispersion.
Subsequently, after treating with a chromato disc, 1 ml of the
dispersion was put into a 10 ml mess-flask, 1 ml of a 1000 ppm
sulfite ion solution was added and ultrapure pure water was added
to make up a solution of 10 ml. The quantity (mg/g sample) of
iodide ions contained in the solution containing ethanol-soluble
components was determined through ion chromatography.
[0098] The thus obtained results are shown in Table 1.
1 TABLE 1 Characteristic Value Precursor Pattern Yield Washing No.
No. (%) Degree (mg/g) Remark 1 -- 33 1.89 Comp. 2 8 84 1.25 Inv. 3
1 73 1.31 Inv. 4 3 79 1.27 Inv. 5 6 74 1.29 Inv. 6 7 82 1.25 Inv. 7
9 80 1.26 Inv. 8 4 78 1.31 Inv. 9 8 95 1.19 Inv. 10 8 75 1.31 Inv.
11 8 85 1.23 Inv. 12 8 85 1.25 Inv. 13 8 60 1.64 Comp. 14 -- 57
1.71 Comp. 15 -- 42 1.97 Comp.
[0099] As apparent from Table 1, it was proved that precursors of
europium activated barium fluoroiodide phosphors (BaFI:Eu
particles), prepared in the process according to this invention
were obtained at a high yield, exhibiting superior washability and
high purity, compared to samples of comparison.
Example 2
[0100] Similarly to Example 1, particulate precursors of europium
activated barium fluorobromide phosphors (BaFBr:Eu particles) were
prepared, except that BaI.sub.2 was replaced by BaBr.sub.2. The
thus prepared precursors were evaluated similarly to Example 1 with
respect to yield and purity. As a result, it was proved that
precursors of europium activated barium fluorobromide phosphors,
prepared in the process according to this invention were obtained
at a high yield, exhibiting superior washability and high
purity.
* * * * *